希夫碱钴配合物的氧合动力学

用红外光谱和循环伏安法证实了Ｃｏ／Ｏ２１：１的氧含物的生成，并确定形成类超氧型的键合氧．在恒定氧压下，Ｃｏ［４－ＯＨＳａｌｅｎ］和Ｃｏ［４－ＯＨＳａｌｐｈ］在ＤＭＦ和ＤＭＳＯ溶剂中氧合反应的级数对配合物浓度为一级，测定了反应速率常数及表观活化能，讨论了氧合机理．

Hot corrosion behavior of Ni-xCr-6.8Al based alloys

The hot corrosion behaviors of as-cast and preoxidized Ni-xCr-6.8Al based alloys in the mixture of Na2SO4＋25% NaCl at 873 K were studied. The results show that the mass loss of Ni-xCr-6.8Al based alloys decreases with the increase of Cr content. Preoxidation improves the resistance to corrosion regardless of the concentration of Cr. The kinetics of as-cast Ni-12Cr-6.8Al and Ni-16Cr-6.8Al based alloys fits the parabolic law well, while that of the as-cast Ni-20Cr-6.8Al based alloy fits the power law. The kinetics of all the preoxidized samples obey the logarithmic law. The mechanism of the as-cast alloys can be well explained by the acid-base melting model. The behavior of the preoxidized alloys is found to be mainly determined by the properties of the oxide layer formed during the preoxidation to a large extend.

Oxidation behavior and mechanism of porous nickel-based alloy between 850 and 1000 °C

The oxidation behavior and mechanism of a porous Ni?Cr?Al?Fe alloy in the temperature range from850to1000°Cwere investigated by optical microscopy,scanning electron microscopy(SEM)and energy dispersive spectroscopy(EDS),X-raydiffraction(XRD)analyses and X-ray photoelectron spectroscopy(XPS).The results show that the oxidation kinetics at950and1000°C of this porous alloy is pseudo-parabolic type.Complex layers composed of external Cr2O3/NiCr2O4and internalα-Al2O3areformed on the surface of the oxidized porous alloys.γ?phases favor the formation of NiO/Cr2O3/NiCr2O4during the initial oxidation.Many fast diffusion paths contribute to the development of the oxide layers.The decrease of the open porosity and the permeabilitywith exposure time extending and temperature increasing can be controlled within a certain range.

Microbial oxidation of refractory gold sulfide concentrate by a native consortium

A defined mesophilic consortium including an iron oxidizing bacterium and a sulfur oxidizing bacterium was constructed to evaluate its ability for bioleaching a flotation concentrate from Andacollo mine in Neuquén,Argentina.Experiments were performed in shake flasks with a pulp density of10%(w/v),using a basal salt medium containing ferrous iron at pH1.8.The leaching solutions were analyzed for pH,redox potential(using specifics electrodes),ferrous iron(by UV-Vis spectrophotometry)and metal concentrations(by atomic absorption spectroscopy).The results showed that the consortium was able to reduce the refractory behavior of the concentrate,allowing91.6%of gold recovery;at the same time,high dissolution of copper and zinc was reached.These dissolutions followed a shrinking core kinetic model.According to this model,the copper solubilization was controlled by diffusion through a product layer(mainly jarosite),while zinc dissolution did not show a defined control step.This designed consortium,composed of bacterial strains with specific physiological abilities,could be useful not only to optimize gold recovery but also to decrease the leachates metallic charge,which would be an environmental advantage.

Isothermal oxidation behavior of TiAl intermetallics with different oxygen contents

Isothermal oxidation behaviors of Ti-45Al-2Fe-2Mo-1Cr intermetallics with different oxygen contents were studied under the condition of 950 °C, 100 h in air, and the oxidation kinetic parameters were also evaluated. The results show that the oxidation resistance of the TiAl intermetallics is negatively related to the oxygen content, and both the mass gain and thickness of oxide scale increase with the oxygen content. The sub-surface microstructure of the oxide scales varies with the oxygen content. Z phase is observed in the sub-surface area of the low-oxygen-content alloy, while the τ2(Al2FeTi) phase is found in the medium-oxygen-content and the high-oxygen-content alloys. The deterioration of oxidation resistance is due to the enhanced internal oxidation with the increase of oxygen content. It is possible to improve the oxidation resistance by controlling the oxygen content.

Leaching of cuprite through NH_4OH in basic systems

Cuprite is a difficult oxide to leach under acidic conditions(for the maximum extraction of50%).In this research,the feasibility of leaching cuprite in an ammoniacal medium was studied.The working conditions addressed here were the liquid/solid ratio(120:1-400:1mL/g),stirring speed(0-950r/min),temperature(10-45℃)and NH4OH concentration(0.05-0.15mol/L).In addition,different ammoniacal reagents(NH4F and(NH4)2SO4)were analyzed.The experiments were performed in a2L reactor with a heating mantle and a condenser.The most important results were that the maximum leaching rate was obtained at pH10.5,0.10mol/L NH4OH,45℃,4h,850r/min and a liquid/solid ratio of400:1,reaching a copper extraction rate of82%.This result was related to the non-precipitation of copper in solution by the formation of copper tetra-amine (Cu(NH2)4^2+).The liquid/solid ratio and stirring speed were essential for increasing the cuprite leaching.The maximum leaching rate was achieved at higher temperatures;however,significant copper leaching rate occurred at temperatures near the freezing point of water(17.9%over4h).Increasing NH4OH concentration and decreasing particle size increased the cuprite leaching rate.The two ammoniacal reagents(NH4F and(NH4)2SO4)had low extraction rate of copper compared with NH4OH.The kinetic model representing cuprite leaching was a chemical reaction on the surface.The order of the reaction with respect to the NH4OH concentration was1.8,and it was inversely proportional to the radius of the ore particles.The calculated activation energy was44.36kJ/mol in the temperature range of10-45℃.

Kinetics of Bulk Polymerization of Octamethylcyclote- trasiloxane

The kinetics of bulk polymerization of octamethylcyclotetrasiloxane under acid circumstance is studied. A kinetic model is put forward and kinetic parameters are obtained through optimization.

Leaching kinetics of antimony-bearing complex sulfides ore in hydrochloric acid solution with ozone

The leaching kinetics of Sb and Fe from antimony-bearing complex sulfides ore was investigated in HCl solution by oxidation?leaching with ozone.The effects of temperature,HCl concentration,stirring speed and particle size on the process were explored.It is found that the recoveries of Sb and Fe reach86.1%and28.8%,respectively,when the reaction conditions are4.0mol/L HCl,900r/min stirring speed at85°C with<0.074mm particle size after50min leaching.XRD analysis indicates that no new solid product forms in the leaching residue and the leaching process can be described by shrinking core model.The leaching of Sb corresponds to diffusion-controlled model at low temperature(15?45°C)and mixed-controlled model at high temperature(45?85°C),and the apparent activation energies are6.91and17.93kJ/mol,respectively.The leaching of Fe corresponds to diffusion-controlled model,and the apparent activation energy is1.99kJ/mol.Three semi-empirical rate equations are obtained to describe the leaching process.

Preparation of Fe-Mn/K/Al2O3 Fischer-Tropsch Catalyst and Its Catalytic Kinetics for the Hydrogenation of Carbon Monoxide

A K promoted iron-manganese catalyst was prepared by sol-gel method,and subsequently was tested for hydrogenation of carbon monoxide to light olefins.The kinetic experiments on a well-characterized Fe-Mn/K/Al2O3 catalyst were performed in a fixed-bed micro-reactor in a temperature range of 280-380 ℃,pressure range of 0.1-1.2 MPa,H2/CO feed molar ratio range of 1-2.1 and a space velocity range of 2000-7200 h-1.Considering the mechanism of the process and Langmuir-Hinshelwood-Hogan-Watson（LHHW） approach,unassisted CO dissociation and H-assisted CO dissociation mechanisms were defined.The best models were obtained using non-linear regression analysis and Levenberg-Marquardt algorithm.Consequently,4 models were considered as the preferred models based on the carbide mechanism.Finally,a model was proposed as a best model that assumed the following kinetically relevant steps in the iron-Fischer-Tropsch（FT） synthesis：（1） CO dissociation occurred without hydrogen interaction and was not a rate-limiting step;（2） the first hydrogen addition to surface carbon was the rate-determining steps.The activation energy and adsorption enthalpy were calculated 40.0 and -30.2 kJ.mol-1,respectively.

Sustainable synthesis of 5-hydroxymethylfurfural from waste cotton stalk catalyzed by solid superacid-SO4^2-/ZrO2

A sustainable process was explored for the preparation of 5-hydroxymethylfurfural(HMF) by catalytic degradation of the waste cotton stalk. Solid super-acid(SO_4^(2-)/ZrO_2) was used as an efficient catalyst for the degradation of cotton stalk. Both decomposition experiments and kinetic study were conducted for the exploration of degradation condition and kinetics mechanism. The optimized experimental conditions are reaction temperature 503 K, reaction time 75 min and dosage of catalyst 30%(mass fraction) based on the decomposition experiments, under which a maximum yield of 27.2% for HMF could be achieved. Kinetic study was then carried out in the presence of SO_4^(2-)/ZrO_2. The theoretical results indicate that the activation energies for reducing sugar and HMF with catalyst are 96.71 k J/mol, 84.21 kJ/mol in the presence of SO_4^(2-)/ZrO_2, and they are 105.96 k J/mol and 119.37 k J/mol in the absence of SO_4^(2-)/ZrO_2.

Dynamics of liquid-phase catalytic oxidation of hydrogen sulfide removal in rural biogas

Hydrogen sulfide in rural biogas was removed with liquid-phase catalytic oxidation.By using rare earth as catalyst,and sulfosalicylic acid as stabilizer,H2S purification efficiency could increase as high as 96%,and sulfur capacity of the composite solution was about 3 g/L.The results show that purification efficiency was affected by catalyst addition,pH,experimental temperature,and sulfur capacity.The parameters effects on catalytic oxidation were studied,and the optimized conditions were that Fe3+ concentration 0.08 mg/L,reaction temperature 70°C,pH 9.0,with a absorption solution volume of 50 mL,a gas flow rate 200 mL/min,and H2S mass concentration of 1.58-2.02 mg/m3.

1T′‐MoTe_(2) monolayer:A promising two‐dimensional catalyst for the electrochemical production of hydrogen peroxide

The direct synthesis of hydrogen peroxide(H_(2)O_(2))via a two‐electron oxygen reduction reaction(2e‐ORR)in acidic media has emerged as a green process for the production of this valuable chemical.However,such an approach employs expensive noble‐metal‐based electrocatalysts,which severely undermines its feasibility when implemented on an industrial scale.Herein,based on density functional theory computations and microkinetic modeling,we demonstrate that a novel two‐dimensional(2D)material,namely a 1T′‐MoTe_(2)monolayer,can serve as an efficient non‐precious electrocatalyst to facilitate the 2e‐ORR.The 1T′‐MoTe_(2)monolayer is a stable 2D crystal that can be easily produced through exfoliation techniques.The surface‐exposed Te sites of the 1T′‐MoTe_(2)monolayer exhibit a favorable OOH*binding energy of 4.24 eV,resulting in a rather high basal plane activity toward the 2e‐ORR.Importantly,kinetic computations indicate that the 1T'‐MoTe_(2)monolayer preferentially promotes the formation of H_(2)O_(2)over the competing four‐electron ORR step.These desirable characteristics render 1T′‐MoTe_(2)a promising candidate for catalyzing the electrochemical reduction of O_(2)to H_(2)O_(2).

Research on the Mechanism of Accelerator for Photocurable Resin in 3D Printing

The photopolymerization kinetics of cycloaliphatic epoxide and oxetane with accelerators were investigated with Real-time Fourier transform infrared spectroscopy(RT-FTIR).The consumption rates of epoxy group and oxetane group as a function of time were obtained by monitoring of the absorption peaks in the 789 cm-1 and 981 cm-1.The effect of accelerators type and the accelerating mechanism were discussed.In general,benzyl alcohol and its analogues with electron-donating substituents are useful accelerators for the cationic polymerization of cycloaliphatic epoxide and oxetane.Activated monomer mechanism and free-radical chain-induced decomposition of onium salt cationic photoinitiator account for the observed accelerating effect on the polymerization rate.

Decontamination of Potential Toxic Elements in Sewaged Soils by Inorganic Amendments

This study investigated the feasibility of using some natural clay minerals available in Egypt like kaolinite, bentonite, also using of iron oxide, rock phosphate and mixture of these types to minimize the rate of Ni, Cu, Zn and Mn desorption from sewage soils and to evaluate the effect of these mixtures on Zn equivalent constant values before and after remediation. The obtained results indicated that all mixtures used were minimizing the rate of potential toxic elements （PTE＇s） release from sewage soils compared to control treatment. According to the decreasing order of different treatments, data indicated that application of the mixture treatment of bentonite, kaolinite and rock phosphate （RP） in sewage soils becomes the best treatment compared to other treatments used. However, the lowest and save Zn equivalent constant value which represents the hazard indicator in the study was observed in sewage soil treated with the mixture of bentonite and RP. The kinetic constants of Elovich, modified Freundlich and Hoerl equations, the best fitted models, were significantly decreased compared to control treatments with different percent of minimization according to type of pollutants and remediation material used. To understand the mechanisms of PTE＇s retained in treated sewage soil, distribution study was applied which showed that different pollutants studied were removed to hardly available form different mechanisms of PTE＇s undergo in treated sewage soils were discussed in the study.

Dissolution kinetics of copper from multi-metal copper alloy roasted in oxygen

A kinetic study on the sulfuric acid leaching of multi-metal oxide, which is the product of multi-metal copper alloy with iron trioxide roasted in oxygen, was carried out. The effects of leaching time, stirring speed, sulfuric acid concentration, reaction temperature, and particle size of the multi-metal oxide on the kinetics and mechanism of copper extraction were studied. It was found that the reaction kinetic model about the copper extraction from multi-metal oxide follows the mixed kinetic shrinking core mode： 1/31n（1-X）＋（1-X）-l/3-1=680.5C（H2SO4）0.4297dp0.75115exp（-Ea/RT）t.

Electrochemical impedance spectra of CdSe quantume dots sensitized nanocrystalline TiO_2 solar cells

Quantum dots sensitized nanocrystalline Tit2 solar cells （QDSSCs） are promising third-generation pbotovoltalc devices. In comparison with conventional dye-sensitized solar cells （DSSCs）, the efficiency of QDSSCs is still very low （about 3%）. In this paper, the electrochemical impedance spectroscopy technology has been adopted to investigate the quasi-Fermi level and the cartier dynamics of the colloidal CdSe QDs sensitized Tit2 eletrode with S2-/Sf redox electrolytes and the series resistance of the QDSSCs. In comparison with the conventional DSSCs with I^-3/Г as redox electrolytes, the energy difference between the conduction band edge and the quasi-Fermi levels of the Tit2 films （or the Fermi levels of the redox electrolytes） in QDSSCs has been decreased by about 0.3 V, resulting in the decrease of Voc by this value. The increases of the electrolyte dif- fussion resistance and the charge transfer resistance between Pt counter electrodes and S2-/Sx redox electrolytes were attributed to the decrease of the fill factors. However, the electron lifetime and electron diffussion length for QDSSCs are longer than those for DSSCs due to the retardation of the electron recombination by the adsorbed cysteine at the surfaces of the TiO2 films. It is indicated that electron recombination at the TiO2/electrolyte interface is not the main reason for the lower Jsc of the colloidal QDs sensitized QDSSCs. Improving light harvesting efficiency and photoelectron injection efficiency should be considered in the future for such kind of QDSSCs.